Cultured human glomerular mesangial cells express the C5a receptor.

BACKGROUND

While the association of complement activation and glomerulonephritis has been recognized for decades, the pathogenic mechanisms of complement-mediated glomerular damage are incompletely understood. Expression of the C5a receptor in the kidney suggests that C5a could play a direct role in initiating or promoting glomerulonephritis.

METHODS

Expression of the C5a receptor by cultured human glomerular mesangial cells (HGMC) was examined by immunofluorescence, by FACS analysis and by reverse transcriptase-polymerase chain reaction (RT-PCR). Potential mitogenic effects were examined by analysis of neutral red dye uptake after treatment with recombinant C5a (rC5a). The production of cytokines [interleukin-1 (IL-1), interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1)] and growth factors [transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF-AB)] by mesangial cells stimulated with rC5a was examined by ELISA of cell culture supernatants.

RESULTS

Expression of the C5a receptor by the cultured HGMC was demonstrated by both immunofluorescence and FACS. The presence of mRNA encoding the receptor was confirmed by RT-PCR. Treatment of HGMC in vitro with rC5a resulted in mild cellular proliferation. No IL-1 was detected despite stimulation with up to 100 nM rC5a. Concentrations of IL-8 and TGF-beta did not increase beyond basal levels in control samples at any level of stimulation. Mean MCP-1 concentrations and PDGF-AB concentrations increased by 40% and 70% above control values 48 hours post-stimulation (P = 0.01 and P = 0.003, respectively).

CONCLUSIONS

These data indicate that the C5a receptor is expressed on HGMC in vitro, and may play a role in mediating glomerular injury by promoting cellular proliferation and the production of cytokines and growth factors.